A. The Field of Invention
The present invention relates to a device for dispensing substance from a cartridge and more particularly to a compact motorized device for dispensing substance from a cartridge with a quick rewind feature.
B. A Description of the Prior Art
Mechanical caulking guns are well known in the field for use in dispensing material from a cartridge. These substance containing cartridges are well known in the construction industry and are generally cylindrical in shape, with a plastic delivery cone attached to one end of the cylinder and a flat, metal, disc-shaped base seal at the other. The disc-shaped base seal is of the same diameter as the cylinder so it may freely slide within the cylinder. When the plastic delivery cone is sliced open at its tip, the front seal behind the delivery cone is pierced, and the disc-shaped base seal is pushed within the cylinder towards the delivery cone, the substance within the cylinder is emitted from the delivery cone.
Currently these cartridges are used with mechanical devices, known as guns, which apply pressure to the disc-shaped base seal at the rear of the cartridge held within the gun. The most widely available guns consist of a holding receptacle for the cartridge, an integrated rod and plunger, and a ratchet mechanism whereby the rod and plunger are advanced though a hand operated lever. Pressure is applied to the disc-shaped base seal of the cartridge through the integrated rod and plunger which is activated in response to the pumping of a trigger on the gun. These mechanical guns can be awkward to use since, quite often, they are used to apply material to a hard to reach place. In such an instance, it is hard for the person using the gun to hold the gun steady while pumping the trigger with his index finger. With repeated use of such a mechanical device, one's hand will quickly become fatigued. The overall configuration of the mechanical gun when it is holding a cartridge is at least twice as long as the cartridge with the trigger midway along the length. The configuration of the conventional gun presents a number of ergonomic problems. Firstly, the rearward extension of the rod over the operator's hand can interfere with the operator's arm movement. Secondly, the excessive overall length of the mechanical gun presents positional problems in confined work spaces. Thirdly, the hand power required leads to arm fatigue and resulting loss of fine control over delivery of the contents of the cartridge. Lastly, at the end of the application of a bead of substance from the cartridge, bead overflow occurs which can only be prevented by the operator manually retracting the ratchet drive. Manual retracting of the ratchet drive makes control over the termination of substance delivery inconsistent and difficult to accomplish.
In the past, attempts have been made to design motorized substance delivery guns, however, these attempts have not cured the problem of having the rod protruding from the back of the loaded gun. In fact, many attempts at motorized devices for dispensing substance from a cartridge have created new problems relating chiefly to the added weight of the motorized unit, but also resulting from the cumbersome method by which the motorized mechanism had to be rewound once substance was delivered from the cone.